【摘 要】 地下连续墙技术起源于欧洲，我国在二十世纪五十年代后期开始在水利部门推广应用这项技术。地下连续墙具有刚度大、防渗好、扰动小、环保等优点，但进行地下连续墙施工需要具有较高的技术水平与施工经验且施工难度较大。本文对地下连续墙在施工中的几个难点进行分析。
【 pick to 】 underground continuous wall technology originated in Europe and in China in the late 1950 s began promoting application of this technology in water conservancy department. Underground continuous wall has great stiffness, good anti-seepage, small disturbance, environmental advantages, but need to carry on the underground continuous wall construction has higher technical level and the construction experience and construction is difficult. In this paper, the several difficulties in underground continuous wall in construction are analyzed.
【关键词】 地下连续墙；施工难点；分析；对策
【 key words 】 underground continuous wall; Construction difficulties; Analysis; countermeasures
1前言
1 introduction
地下连续墙技术起源于欧洲，1950年意大利最先在工程中应用，我国在二十世纪五十年代后期开始应用这项技术。地下连续墙是通过专用的挖（冲）槽设备，沿着地下建筑物或构筑物的周边，按预定的位置，开挖出或冲钻出具有一定宽度与深度的沟槽，用泥浆护壁，并在槽内设置具有一定刚度的钢筋笼结构，然后用导管浇灌水下混凝土，分段施工，用特殊方法接头，使之连成地下连学的钢筋混凝土墙体，其主要用于：基坑开挖和地下建筑的临时性和永久性的挡土结构；地下水位以下的截水、防渗；部分工程的墙体还承受上部建筑的永久性荷载兼有挡土墙和承重基础作用；邻近建筑物的支护；具有振动相邻影响的隔振墙等。
Underground continuous wall technology originated in Europe, Italy in 1950 the first in the engineering application, in the late 1950 s began to application of this technology in our country. Underground continuous wall is through a dedicated to dig (rushed) slot devices, along the surrounding underground buildings or structures, according to the predetermined position, the excavation or impact drill with a range of width and depth of groove, using slurry supporting, and set up around a slot has a certain stiffness of structure of reinforcing cage, and then use catheter pouring underwater concrete, section construction, joint in a particular way, make it into underground reinforced concrete wall, even learn it is mainly used in: foundation pit excavation and the underground construction of the temporary and permanent soil retaining structure; Underground water level below the cutoff, seepage control; Part of the wall still under the upper construction engineering permanent load both retaining wall and bearing basic role; Adjacent building support; Of the impact of adjacent vibration isolation wall, etc.
2地下连续墙施工难点
2 underground continuous wall construction difficulties
地下连续墙的施工过程主要为放样、导墙施工、钢筋笼制作、泥浆制作、成槽、吊装钢筋笼、灌注混凝土。以下将叙述各个重要施工环节中的要点和难点：
Mainly for lofting of underground continuous wall construction process, the guide wall construction, reinforcing cage production, the production of mud, into a trough, hoisting reinforcing cage, pouring concrete. Of the following describes the important link of the construction key points and difficult points:
2.1导墙施工。导墙是地下连续墙施工的第一步，导墙的功能主要为保护槽口及保证槽段位置的准确性，支承施工设备的荷载，支承焊接钢筋笼的接长，蓄浆并调节液面，明确施工位置，防止槽壁顶部的坍塌等。其主要有以下几个问题：
2.1 guide wall construction. Guide wall is the first step on the underground continuous wall construction, the function of the guide wall are mainly protect noth and ensure the accuracy of the slot position, bearing load of construction equipment, supporting long welding of reinforcing cage, slurry storage and adjusting the liquid level, clear the construction location, prevent collapsed on top of the tank wall, etc. The main have the following questions:
2.1.1导墙变形导致钢筋笼不能顺利下放：其主要原因是导墙施工完毕后没有加纵向支撑，导墙侧向稳定性不足，产生导墙变形。解决这个问题的措施是导墙拆模后，沿导墙纵向每隔2米设二道木支撑，将二片导墙支撑起来，导墙混凝土未达到设计强度前，禁止重型机械在导墙侧面行驶。
2.1.1 guide wall deformation in reinforcing cage can't smoothly down: the main reason is the guide wall construction is completed without longitudinal support, guide wall lateral stability is insufficient, the guide wall deformations. The measures to solve the problem of the guide wall is ripping, along the vertical guide wall set two sleeper support every 2 meters, the 2 pieces of guide wall support, guide wall prior to meet the design strength of concrete, heavy machinery in drive on the side of the guide wall is prohibited.
2.1.2 导墙的内墙面与地下连续墙的轴线不平行：由于导墙本身的不垂直，造成整幅墙的垂直度不理想。导墙的内墙面与地下连续墙的轴线不平行会造成建好的地下连续墙不符合设计要求。
2.1.2 the metope inside the guide wall of parallel to the axis of the underground continuous wall not: due to the not vertical guide wall itself, causing the whole picture of verticality of the wall is not ideal. Within the guide wall of metope and the axis of the underground continuous wall not PingHangHui resulted in building underground continuous wall is not in conformity with the design requirements.
2.2成槽。
2.2 into the slot.
2.2.1地下水的升降：遇到降雨等情况使地下水位急速上升，地下水又绕过导墙流入槽段使泥浆对地下水的超压力减小，极易产生塌方事故。为了解决槽壁塌方，必要时降低地下水，保证槽壁的稳定。另一个方法是提高泥浆液面，泥浆液面至少高出地下水位0.5～1.0m。在施工中发现漏浆跑浆要及时堵漏补浆，以保持泥浆规定的液面。
2.2.1 the rise and fall of groundwater: encounter rain, and so on and so forth make the underground water level rose rapidly, groundwater around the guide wall inflow slot again reduce mud on groundwater super pressure, prone to landslides. In order to solve tank wall collapse, if necessary, reduce the groundwater, ensures that the trench wall stability. Another way is to improve the mud slurry surface, mud slurry surface above the underground water level at least 0.5 ~ 1.0 m. Run is found during the construction of slurry grouting plugging filling slurry in time, to keep the liquid level specified by the mud.
2.2.2刷壁次数的问题：刷壁要求在铁刷上没有泥才可停止，以确保接头面的新老砼接合紧密，若达不到要求，可能造成两幅墙之间夹有泥土，产生严重的渗漏，对地下连续墙的整体性也有很大影响。
2.2.2 brush wall the problem: the number of brush wall requires no mud can only stop in the iron brush, to ensure that the new and old concrete bonding joint surface closely, if not reach requirement, can cause between two walls with dirt, severe leakage, also has a great influence to the integrity of the underground continuous wall.
2.3钢筋笼起吊和下钢筋笼。
2.3 reinforcing cage hoisting and reinforcing cage.
2.3.1钢筋笼难以放下：钢筋笼难以放下主要由于两方面的原因：一方面是槽壁变形过大或槽孔施工垂直达不到要求，以及出现坍塌等；另一方面是钢筋笼尺寸不准，纵向接头处产生弯曲吊放时产生变形。其主要解决办法为严格控制钢筋笼外形尺寸，其长宽应比槽孔小100～120mm，钢筋笼接长时使上段垂直对正下段，再进行焊接，并对称施焊，如因槽壁变形过大等钢筋笼不能放入，应将槽孔修整后在放钢筋笼。
2.3.1 reinforcing cage is difficult to put down: reinforcing cage is difficult to put down mainly because of two reasons: on the one hand the trench wall deformation is too large or vertical slot construction can not meet the requirements, and collapse, etc.; On the other hand is a reinforcing cage size, are not allowed to be positioned and longitudinal bending joint deformation. The main solution for the strict control of reinforcing cage shape size, the width should be smaller than slots of 100 ~ 120 mm, reinforcing cage extension made under section vertical to is on the segment, then welding, and symmetrical welding, such as the trench wall deformation is too large for reinforcing cage can't add, slot should be after finishing the reinforcing cage.
2.3.2钢筋笼上浮：钢筋笼上浮主要是因为钢筋笼太轻，槽底沉渣过多，导管埋入深度过大，或混凝土浇灌速度过慢，钢筋笼被托起上浮。其解决办法为钢筋笼在导墙上设置锚固点固定钢筋笼，清除槽底沉渣，加快浇灌速度，控制导管的最大埋深不超过6m。
2.3.2 reinforcing cage up-floating: reinforcing cage up-floating mainly because of reinforcing cage is too light, groove bottom sediment is overmuch, catheter embedment depth is too big, or concrete casting speed too slow, reinforcing cage provide buoyancy. Its solution set for anchor point for reinforcing cage in the guide wall reinforcing cage, remove dreg deposited at the bottom of the tank, to speed up the casting speed, the control tube maximum buried depth of less than 6 m.
2.3.3钢筋笼的吊放：钢筋笼的吊放过程中，笼在空中摇摆，吊点中心与槽段中心不重合。就会造成吊臂摆动，使笼在插入槽内碰撞槽壁发生坍塌，吊点中心与槽段中心偏差大，钢筋笼不能顺利沉放到槽底等。
2.3.3 reinforcing cage hanging put, sling the process of reinforcing cage, cage swing in the air, the lifting point center and slot center does not coincide. Can cause swing boom, the cage in the insertion slot collision groove wall collapsed, lifting point center center big deviation with the slot and reinforcing cage can't smooth sink into the bottom of the channel, etc.
2.4下、拔混凝土导管、浇筑混凝土。
2.4, ducts, concrete pouring concrete.
2.4.1导管拆卸的问题：在浇筑混凝土时，要根据计算逐步拆卸导管，但由于有些导管拆不下来或需要很多的时间拆卸，严重的影响了混凝土灌注。其解决方法为只要每次混凝土灌注完毕把每节导管拆卸一遍，螺丝口涂黄油润滑。还应注意在使用导管时，防止导管碰撞变形，难以拆卸。
Against 2.4.1 catheter removal problem: when pouring concrete, shall be calculated according to gradually remove catheter, but due to some catheter break down or need a lot of time down, and the serious influence of concrete. The solution for as long as you put each section after each concrete perfusion catheter removal again, screws and butter lubrication. Also should pay attention to when using catheter to prevent vessel collision deformation, difficult to remove.
2.4.2槽底淤积物对墙体质量的影响：槽孔底部淤积物是墙体夹泥的主要来源。混凝土开浇时向下冲击力大，混凝土将导管下的淤积物冲起。当多根导管同时浇注时，导管间混凝土分界面也可能夹泥，这些夹泥大多来自槽底淤积物。在浇筑过程中，对采用两根导管的地下连续墙，砼浇注应两根导管轮流浇灌，确保砼面均匀上升，砼面高差小于50cm。以防止因砼面高差过大而产生夹层现象。
2.4.2 groove bottom warp on the quality of the wall: warp is at the bottom of the slot wall of mud main source. Concrete cast starting down the huge impact, concrete will warp rushed up the catheter. When multiple catheter placement at the same time, catheter between the concrete interface may also be mud, most of these clamps mud from the bottom of the channel warp. In casting process, to use two catheter of underground continuous wall, concrete pouring should be two catheter irrigation in turn, ensure uniform concrete surface rise, concrete surface elevation difference is less than 50 cm. In order to prevent the intercalation phenomena due to concrete surface elevation difference is too large.
2.5槽壁坍塌。地下连续墙槽壁坍塌主要原因有以下几方面：①遇软弱土层或流沙层；②护壁泥浆选择不当、泥浆密度不够、泥浆水质不符合要求，易于沉淀，起不到护壁作用；③地下水位过高或孔内出现承压水；④在松软砂层中进尺过快或空钻时间过长；⑤成槽后搁置时间过长，泥浆沉淀。
2.5 tank wall collapsed. Underground continuous wall groove wall collapsed main reason has the following several aspects: (1) in soft soil layer or quicksand layer; Improper selection (2) retaining wall mud, mud density, mud water quality does not meet the requirements, easy to precipitate, no breast wall; (3) the underground water level is too high or hole in confined water; (4) in the soft sand penetration too quickly or empty drilling time is too long; (5) into a slot on hold after a long time, mud precipitation.
基于以上几个原因其相应的解决办法为：慢速钻进；适当加大泥浆密度成槽应根据土质情况选用合适泥浆，并通过试验确定泥浆密度；控制槽段液面高于地下水位0.5m以上；控制进尺，不要过快或空转过久；槽段成孔后，及时放钢筋笼并浇灌混凝土。
Based on the above several reasons for its corresponding solution are: slow drilling; Increase mud density appropriately into slot should be selected according to soil conditions appropriate mud, and mud density determined by test; Control slot liquid level is higher than 0.5 m above the underground water level; Control footage, don't be too fast or idling for too long; Trough Duan Chengkong, timely put reinforcing cage and placing of concrete.
随着工业和城市建设的发展，以及城市用地的紧张，要求更多地对地下空间开发与利用，同时高层建筑、地铁、港口等地下构筑物的建设，要求地下构筑物和基础埋置深度越来越深，所承担的荷载越来越大。地下连续墙具有刚度大、防渗好、扰动小、环保等优点，但进行地下连续墙施工需要具有较高的技术水平与施工经验，因此在施工中我们应根据不同的地质情况来选择相应的施工方法和机械以达到良好的效果。
Along with the development of industry and urban construction, and urban land tensions, demanding more under the surface-to-surface space development and utilization, and high-rise buildings, subways, port, etc. The construction of underground structures, demand more and more deep underground structures and foundation embedment depth, to load more and more big. Underground continuous wall has great stiffness, good anti-seepage, small disturbance, the advantages of environmental protection, carry on the underground continuous wall construction but need to have a high technical level and the construction experience, therefore in the construction we should according to different geological conditions to select the corresponding construction methods and machinery in order to achieve good results.